1. Field of the Invention
The present invention relates to a motor device applicable to a system such as a vehicle power window apparatus in which a transmission mechanism is employed for transmitting rotational driving force.
2. Description of Related Art
Conventionally, as shown in FIG. 6, in a motor device of a vehicle power window apparatus for opening and closing a side window glass of a vehicle door, rotational driving force of a motor 50 is transmitted through a motor output shaft with a worm (not shown) to a worm wheel 51. The driving force transmitted to the worm wheel 51 is further transmitted via a rubber damper 52 to an output plate 53 and an output shaft 54.
The worm wheel 51, the output plate 53 and the output shaft 54 are arranged to rotate in a same center axis. As shown in FIG. 7, the worm wheel 51 is housed in a wheel accommodating recess 55a of a gear housing 55 and is rotatably held by a bearing portion 56 protruding out of a bottom of the recess 55a. The rubber damper 52 is housed in a damper accommodating ring shaped recess 51a opened upward in the worm wheel 51. The output shaft 54 is rotatably held in a shaft receiving hole 56a provided in the bearing portion 56 and supports the output plate 53 arranged at an opening axial end of the damper accommodating recess 51a. Each of engaging portions 51b of the worm wheel 51 is engaged via each of damper portions 52a of the rubber damper 52 with each of engaging projections 53a of the output plate 53 so that the rotational driving force is transmitted from the worm wheel 51 to the output plate 53.
The output plate 53 is formed by press stamping a metal sheet. The output plate 53 is provided in a center thereof with a shaft receiving hole 53b formed by stamping. As shown in FIG. 8, a shaft inserting portion 54a of the output shaft 54 is fitted to the shaft receiving hole 53a. The engaging projections 53a are formed by bending downward outer circumferential parts of the output plate 53 so as to form notches or holes adjacent thereto.
When the motor 50 rotates to drive the side window glass upwardly and, then, the side window glass comes in contact with a window frame so that the upward movement of the side window glass is suddenly restricted, a rotation of the output plate 53 is restricted. The restriction of the output plate 53 causes a restriction of rotation of the worm wheel via the rubber damper 52. The rubber damper 52 absorbs reaction force suddenly acting against the worm wheel 51 or the motor 50 so that a shock to the motor 50 is eased.
The conventional motor device has a drawback that fitting of the output plate 53 to the output shaft 54 is likely to loose as a clearance therebetween is formed circumferentially during an actual use. The rotational driving reaction force causes to deform the shaft receiving hole 53b of the output plate 53 so that that the clearance is circumferentially formed. That is, a construction of the shaft receiving hole 53b of the output shaft 53 does not have sufficient strength to endure large force applied from the shaft inserting portion 54a of the output shaft 54 to the shaft receiving hole 53b at a time during which the shock is absorbed.
To cope with this problem, it may be contemplated to employ the output plate 53 whose material sheet thickness is thicker or whose material strength is stronger so that the shaft receiving hole 53b is unlikely to deform. However, press stamping a metal sheet having thicker thickness or stronger strength is more difficult, resulting in shortening a lifetime of pressing equipment and reducing dimensional accuracy of the output plate or increasing material cost.
An object of the invention is to provide a transmission mechanism having an output plate and an output shaft for transmitting rotational driving force from the output plate to the output shaft in which fitting of the output shaft to the output plate is unlikely to loose during an actual use.
It is another object of the invention to provide a motor device having the transmission mechanism thereof.
To achieve the above object, a transmission mechanism for transmitting rotational driving force has a driven member rotating upon receiving the rotational driving force, an output plate having a flat surface and engaged with the driven member to rotate together therewith, and an output shaft.
The output plate is integrally provided in a center thereof with a linking portion axially extending by a length longer than thickness of the flat surface. The linking portion has a shaft receiving hole with a plurality of engaging surfaces extending axially for receiving circumferentially the rotational driving force. The output shaft is provided at an axial end thereof with a shaft inserting portion fitted to the shaft receiving hole so that the output shaft penetrates the driven member and is connected to the output plate so as to rotate together therewith in a state that an axial length of the shaft inserting portion in contact with each of the engaging surfaces is longer than the thickness of the flat surface.
In a case of a motor device having the transmission mechanism, the motor device is composed of a motor, a gear housing fixed to the motor and provided in a center thereof with a bearing, a wheel housed in the gear housing and driven to rotate around the bearing by the motor, a damper housed in the recess to rotate together with the wheel, an output plate having a flat surface and engaged with the damper to rotate via the damper together with the wheel, and an output shaft rotatably held in the bearing.
The wheel is provided on a surface thereof perpendicular to a center axis of the bearing with a recess. The output plate is integrally provided in a center thereof with a linking portion axially extending by a length longer than thickness of the flat surface. The linking portion has a shaft receiving hole with a plurality of engaging surfaces extending axially for receiving circumferential force. The output shaft is provided at an axial end thereof with a shaft inserting portion fitted to the shaft receiving hole so that the output shaft penetrates the wheel and the damper and is connected to the output plate so as to rotate together therewith in a state that an axial length of the shaft inserting portion in contact with each of the engaging surfaces is longer than the thickness of the flat surface. With the motor device mentioned above, the wheel and the damper correspond to the driven mechanism of the transmission mechanism.
According to the transmission mechanism or the motor device mentioned above, reaction force from the output shaft is applied to axially extending wide areas of the engagement surfaces so that stresses are not concentrated to a limited area thereof. Accordingly, the linking portion scarcely deforms so that the fitting of the output shaft to the output plate is unlikely to loose during an actual use, even if the output plate is formed by press stamping a metal sheet whose sheet thickness and material strength are similar to the conventional metal sheet.
It is preferable that the linking portion is formed in shape of a composite pipe having inside and outside walls which are folded down each other. The outside wall extends to protrude out of the flat surface toward the driven member and the inside wall, which is formed in cylindrical shape, extends perpendicularly to the flat surface in a direction opposite to the driven member through an inside of the outside wall.
Preferably, the inside wall extends up to a position exceeding a surface of the flat surface on an opposite side to the driven member so that both axial ends of the inner wall are positioned on opposite sides of the flat surface.
Accordingly, structural strength of the linking portion is sufficiently reinforced, axial length of the transmission mechanism is effectively limited.
Further, it is preferable that the output plate is integrally provided at outer periphery of the flat surface with engaging projections protruding on a side of the damper with grooves extending radially at given angular intervals on the flat surface on an opposite side to the damper, the engaging projections being circumferentially engaged with the damper. Since notches or holes, which are opened downward and adjacent to the engaging projections, are not formed, the damper never warp toward the output plate so as to partly enter into the notches or holes, when the rotational driving reaction force is applied circumferentially from the engaging projections to the damper portions, as shown in the conventional output plate. Therefore, the damper is elastically deformed only in a circumferential direction with respect to the center axis thereof so that the damper may absorb more surely the reaction force that is remarkably large.
Furthermore, preferably, the bearing is provided at an axial end thereof with a recess in which the linking portion is partly accommodated. The wheel and the output plate are partly overlapped in an axial direction. Accordingly, while an axial length of the output shaft or the transmission mechanism becomes shorter or compact, the axial length of the bearing for supporting the wheel becomes longer so that more stable rotation of the wheel may be secured.